Bump undici from 5.25.2 to 5.26.3 in /tests/worker

Bumps [undici](https://github.com/nodejs/undici) from 5.25.2 to 5.26.3.
- [Release notes](https://github.com/nodejs/undici/releases)
- [Commits](nodejs/undici@v5.25.2...v5.26.3)

---
updated-dependencies:
- dependency-name: undici
  dependency-type: indirect
...

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